The Temuka Leader. THURSDAY, MARCH 20, 1884. WHAT FARMERS OUGHT TO KNOW.

Temuka Leader, Issue 1154, 20 March 1884, Page 2

The Temuka Leader. THURSDAY, MARCH 20, 1884. WHAT FARMERS OUGHT TO KNOW.

AGRICULTURAL CHEMISTRY. ( Written specially for this Paper.) VII. DRAINAGE. Drainage is one of the mechanical means for improving soils. An excessive quantity of water on land is destructive of vegetation, and in many cases a sufficient natural outlet for the water does not exist ; accordingly artificial drainage has to be resorted to. Sandy soils, being light and porous, do not retain water as heavy clay soils do, thus the latter require the artificial removal of water more than the former. And now, as to some of the principal benefits to be derived from drainage. It is necessary that air, with that übiquitous and most needful element, oxygen, should penetrate the soil, but when water occupies the channels and pores by which it would enter, it cannot. In this way, one of the principal means employed by nature to keep the soil healthy, so to speak, is frustrated, and the land in course of time becomes infertile. In addition to this, water lying any length of time on the ground is stagnant, and all sorts of injurious compounds are formed. When rain falls on land containing already excess of water the percolation of the rain water laden with valuable salts is prevented. In this way those materials the rain contains are lost to the soil, at least they can afford no immediate benefit. It is a well known fact that when any liquid evapoiates, cold is invariably produced. This is the principle of our Hygrometers. Now, if water be evaporating, the soil must necessarily be cooled, and in some case;, much below the heat it requires. Cold, we all know, is detrimental to germination, and in this way excess of water acts most injuriously. These are some of the negative reasons why the drainage of land on which excess of water lies, should be resorted to.

Drainage opens up the soils, loosens it, and makes it more porous. The land being porous, and kept in a more porous state than otherwise by drainage, the sweet fresh air can gain easy access, and effect the many necessary changes required by nature. The ground is warmer, and more suitable to receive the seed. Again well drained land is able to get rid of excess of water after heavy rains ; and its being in such a state helps the very necessary percolation of water through it, and this induces porosity and makes it looser. Rain water often contains oxygen; in this way this element is sometimes introduced into the soil, to accomplish the same things that air does. Water is often warmer than the soil it enters, and it gives up part of its heat to the soil. The soil’s looseness aids the plant when searching for its food. The roots penetrate more deeply and with greater ease. Manures have greater effect on drained than on undrained land. From the above enumeration of the benefits of drainage little doubt can be entertained but that “ it is the first and most important means at our disposal for the improvement of all descriptions of land in which an undue proportion of water prevails.” One deleterious effect of drainage is that it removes many soluble material present in the soil. The analyses of drainage water show that some valuable salts are carried away, and especially nitrates. These are very soluble, and their removal is injurious to the soil, since they form, as we have seen, part of the most valuable food of plants. Ploughing. The effects of this operation need little notice, since they are so well known. In the first place it breaks up the land making it more porous, and better adapted for vegetable growth ; secondly it exposes a large surface of the soil to the action of the atmosphere, frost and rain, all of which induce porosity and looseness. The porosity of soil has a very great deal to do with its productiveness, and thus, by exposing a large surface to the action of these natural agents, that would not otherwise reach to the depth of soil turned up, the fertility of the land is improved. The manner in which rain, frost, ice, carbonic acid, and oxygen effect disintegration of rock and soil has been already explained, and it is unnecessary to recur to the subject. From what has been already said a clear idea ought to have been obtained how the soil is made to crumble away and become porous and loose. And now as to the various claims of deep and shallow ploughing on the farmer. The soil, we have seen, is composed of mineral and organic matter, the organic matter is obtained from the decay of vegetable and animal organisms in the ground. The subsoil is decayed and disintegrated rock, the soil is decayed and disintegrated rock, jphfs organic constituents. The soil, generally speaking, will grow plants ; the subsoil not, because there is no organic matter present. Now, in shallow ploughing we are dealing with a very limited supply of inorganic or mineral substances, consequently if there is no means of replenishing the land with what is removed, our supply must run out. One of the means of replenishing this exhaustion is by means of deep ploughing. The deeper the plough penetrates tlie larger the amount of mineral matters it turns up and affords the plant, presuming of course that the subsoil contains—as the majority do—mineral and innoxious substances. In this way it is sufficiently plain that deep is superior to shallow ploughing.

Deep ploughing again loosens a greater depth of soil and thus facilitates the maturing of plants, since their roots, as a rule, do not go much below the depth of the plough. With deeper ploughing a greater amount of mineral matter is afforded the crop, and caeteris paribus a greater quantity of grain can be raised from land that has received a good deep ploughing than from that which has received shallower treatment, not only from the fact that there is a greater supply of food present, but that plants are able to extend their roots to a greater depth to obtain such food. The large supply will admit of more grain being raised (over a number of years), and the facility with which tha plant can obtain Its food may probably bring it to a better maturity.

The benefit of deep ploughing must be great to light soils that have been manured, since owing to the percolation of water through them a considerable quantity of the soluble components of manures must be carried into the subsoil. The recovery of many valuable fertilisers, from the subsoil forms another argument in favor of deep ploughing. The following is from a great authority on the subject of Agriculture, Mr Stephens “ Shallow ploughing for a seed furrow is common in the case of fields of grass that have been pastured by sheep, and their droppings form too good a top dressing to be buried by deep ploughing. The reason is plausible but may be questioned. It is well known that the roots of plants push themselves everywhere in pursuit of nutriment, even through media which afford little nourishment, in order to reach the one instinctively in which they can luxuriate. With the largest vegetable productions, as trees, this is remarkably the case ; and wth cereals the roots are known to extend to six feet and more, into the subsoil. Hence a strong argument for deep ploughing. In all shallow ploughing the weeds exert an ascendency over the crops. To plough deep atonceinto a subsoil of sand or gravel impregnated with oxide of iron, might run the risk of injuring the scanty upper soil. But such a soil has a tendency to pan, which deep ploughing ing alone can destroy, by breaking it up and exposing it to the air which converts the iron into a harmless peroxide.” Mr Stephens, it will be noticed, deals only with exceptional cases, where shallow ploughing would be expected to be preferable ; and even in tnese cases he does not seem to doubt the efficacy of the deeper treatment. The different effects of deep ploughing ot course depends on the nature and character of the soil and subsoil, and no rigid rule can be laid down, only that, generally speaking, deep is more efficacious than shallow ploughing. The deeper the land is ploughed the more it costs, and thus it is a somewhat pecuniary disadvantage to the farmer. This is a present disadvantage, and although it may cost a little more than the shallow treatment, tha land will last a good deal longer, and more grain on the whole can be raised from land which has been deep ploughed than that which has received shallow ploughing. In prospective, deep ploughing is a very great advantage, but, as we have said, it depends on the character of the soil and subsoil. {To he Continued.)